Organic and inorganic processes commonly require the use of sensor systems having a sensor in the process solution. For example, in many processes, the pH of the process must be continuously measured. In other processes the amount of dissolved oxygen is critical, and must be continuously monitored. Both pH and DO sensors have a membrane separating the sensor electrolyte from the process solution, while other sensors include optical windows. A major problem in such systems is the fouling of the sensor membrane or window. In organic processes containing cellular growth products, growth of cells on the sensor membrane may occur, causing incorrect sensor readings, as well as failure of the sensor. Other processes may deposit oil or other contaminant films on the membrane. In a process solution having significant hydroxide concentrations, common salts, such as copper, iron, or calcium precipitate on the sensor membrane.
In the prior art, fouling of the sensor has been corrected by halting the process, removing the sensor for cleaning, and thereafter replacing the sensor. Known on-line cleaning technology has proved to be expensive and not very reliable. Thus, there is a need for apparatus and method for quickly, accurately, and economically cleaning fouled sensors in situ.